Question PC won't boot unless power button on motherboard pressed

[exeleon]

Not sure if this belongs here or not, as I'm unsure if this is a PSU or motherboard issue. My title pretty much explains what is happening. My PC won't wake or power back on after a full shutdown (it does restart just fine). The power button on the case does not start it all. The only way to get it to boot back up is to take the side panel off the case and press and hold the tiny power button directly on the motherboard. My first thought was a faulty power button so I swapped everything into a new case (I had a new case laying around) however this did not resolve the issue. What are some troubleshooting steps to determine if the issue is the PSU, motherboard or elsewhere?
Here are some specs:

• ASUS Z97-A LGA 1150 Intel Z97 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard
• Rosewill ARC Series, ARC 750, 750W Non-Modular Power Supply, 80 PLUS BRONZE Certified
• Intel Core i7-4790K
• G.SKILL Ripjaws X Series 8GB
• MSI GeForce GTX 970

 

[Lutfij]

The only way to get it to boot back up is to take the side panel off the case and press and hold the tiny power button directly on the motherboard.
Are you referring to the button located above the 24pin main connector, listed in your motherboard manual's PCB layout diagram, here, page 1-2? if so, that's the Mem-OK button, what slots are the sticks of ram populating on the board? BIOS version for your motherboard? Also, does your time on the motherboard get reset? If so, try and replace the CMOS battery on the board with a fresh cell.

How old is the PSU in the build?

To rule out a faulty switch on any case, disconnect the front panel case buttons from the motherboard, then use a flat head screwdriver to momentarily make contact with the +ve and -ve terminals on the board's front panel.

^ for reference only, use your motherboard's manual to identify which pins are for power and which is the positive(+ve)/negative(-ve) terminals.

 

[exeleon]

The only way to get it to boot back up is to take the side panel off the case and press and hold the tiny power button directly on the motherboard.
Are you referring to the button located above the 24pin main connector, listed in your motherboard manual's PCB layout diagram, here, page 1-2? if so, that's the Mem-OK button, what slots are the sticks of ram populating on the board? BIOS version for your motherboard? Also, does your time on the motherboard get reset? If so, try and replace the CMOS battery on the board with a fresh cell.

How old is the PSU in the build?

To rule out a faulty switch on any case, disconnect the front panel case buttons from the motherboard, then use a flat head screwdriver to momentarily make contact with the +ve and -ve terminals on the board's front panel.

^ for reference only, use your motherboard's manual to identify which pins are for power and which is the positive(+ve)/negative(-ve) terminals.

Hey thanks for the reply! The PSU and all of the other components in this build were all purchased in 2015 however the issue didn't start occurring until 2019. I'm really hoping it's the PSU because it's been hard to come by a motherboard with the socket needed for this CPU. Is the best way to test the PSU just to try a new one?